1. Field of the Invention
The present invention relates to a hardness tester.
2. Description of Related Art
Conventionally, a hardness tester (such as a Vickers hardness tester, a Rockwell hardness tester, and the like) is known which measures hardness of a sample by applying a test force to a surface of the sample using an indenter having a planar rhomboid shape or an indenter having a conical or spherical tip to form a polygonal indentation. For example, in a case of a lever-type hardness tester, a weight is used to apply the test force to the surface of the sample.
Specifically, as shown in FIG. 10, in a conventional hardness tester 101, a load lever 102 rotates due to a force of gravity acting on a weight 103 and a predetermined load is applied to an indenter column 104a having an indenter 104 at a forefront end thereof. Then, the load applied to the indenter column 104a is transmitted to the indenter 104 to become a test force for forming the indentation in a sample S placed on a sample stage 105. The weight 103 of the hardness tester 101 has a plurality of weights 1031, 1032, and 1033 stacked on top of each other in a vertical direction and also has a shaft member (or shaft) 161 running through a hollow portion of each of the weights 1031, 1032, and 1033. Therefore, the weight 103 of the hardness tester 101 has a shape long in the vertical direction.
In addition, as shown in FIG. 11, a hardness tester 201 is also known in which a shape of a weight 203 is more compact in the vertical direction as compared to the weight 103 of the hardness tester 101 (see, e.g., Japanese Patent Laid-open Publication No. 2006-226883).
However, the indenter is a component formed by an expensive material such as diamond and, in order to prevent damaging accidents and the like due to contact with the sample, a large distance must be kept between a tip of the indenter and the sample during standby for a test. When a large distance is kept between the tip of the indenter and the sample, a distance to the sample when performing the test becomes large, and thus the indenter column must have a greater stroke. Because the indenter column is subject to an action of the load lever, when the stroke of the indenter column is made larger, a rotation amount of the load lever naturally increases. In the conventional case of the hardness tester 101 shown in FIG. 10, for example, in order to apply a load to the indenter 104 with various test forces by combining only the weight 1031, or the weights 1031 and 1032, or the weights 1031, 1032, and 1033, a size of a gap P1 between the weights 1031, 1032, and 1033 must be at least an action stroke or more of the weight 103 due to rotation of the load lever 102. Therefore, when the stroke of the indenter column 104a is increased, the action stroke of the weight 103 due to the rotation of the load lever 102 is increased by an amount of leverage and the size of the gap P1 is further amplified by a number of layers of the weights 103. For example, in a case where the leverage is multiplied by ten and the weights 103 have ten layers, when attempting to amplify the stroke of the indenter column 104a by 1 mm, a space of 1 mm×10 (multiplier)×(10−1) (layers)=90 mm must be reserved. Therefore, there is a problem that the entire tester cannot be made compact.
In addition, in the conventional case of the hardness tester 201 shown in FIG. 11, the weight 203 can be made compact in the vertical direction. However, there is a problem that a horizontal-direction position of the weight 203 cannot be made stable. Specifically, as shown in FIG. 12, weights 2031, 2032, and 2033 each have a margin of horizontal-direction shifting the size of a horizontal-direction gap P2 between each of the weights 2031, 2032, and 2033. In a case where repeated hardness tests are conducted, for example, shifting of the horizontal-direction position of each of the weights 2031, 2032, and 2033 may occur with respect to a shaft member 261, which serves as a positioning reference, and there may be interference between the weights being used for the load and the unused weights. Therefore, there is a risk that a correct test force may be impossible to generate.